1. Field of the Invention
The present invention relates to a segment for a rehabilitating pipe assembly, and more particularly to a segment that is coupled to additional segments to constitute a rehabilitating pipe assembly for rehabilitating an existing pipe such as a sewer pipe.
2. Description of the Prior Art
A method of rehabilitating an existing pipe is known from Japanese Published Patent Application No. 2003-286742 and the like, wherein a compound pipe is constructed to rehabilitate an existing pipe, such as a sewer pipe, by assembling inside an existing pipe a rehabilitating pipe whose outer diameter is slightly less than the inner diameter of the existing pipe, and then filling and hardening a filler in the gap between the outer periphery of the rehabilitating pipe and the inner wall surface of the existing pipe. The rehabilitating pipe is a circular pipe assembled, as shown in FIG. 20 for cases wherein the diameter is approximately 1,000–1,800 mm, by an assembly worker S who assembles, inside a manhole in communication with the existing pipe, short ring-shaped pipe units 2 that constitute the rehabilitating pipe 3 by coupling a plurality of segments 1 in a direction corresponding to the circumferential direction of the rehabilitating pipe 3, and then carrying these pipe units 2 into the existing pipe and successively coupling them in the longitudinal direction (hereinafter, referred to as ring assembly).
Since ring assembly is problematic for the case wherein the rehabilitating pipe 3 has a large diameter of approximately 2,000 mm or greater, as shown in FIG. 21, or the case wherein the rehabilitating pipe 3 is a rectangular pipe, as shown in FIG. 22, the worker S assembles the rehabilitating pipe 3 inside the existing pipe by successively coupling the segments 1 in units, one by one, in the longitudinal direction and the circumferential direction of the rehabilitating pipe 3 (hereinafter, referred to as segmental assembly).
Each segment 1 has an inner plate that constitutes an inner circumferential surface of the rehabilitating pipe 3, and in this inner plate at both end parts are formed rectangular openings (refer to the openings 101a in FIG. 4) for performing the work of mutually coupling the segments 1 with bolts and nuts in a direction corresponding to the circumferential direction of the rehabilitating pipe 3. After the completion of the mutual coupling of the segments in the circumferential direction by the existing pipe rehabilitation work, a cover is fixed to the opening to plug it. The following methods are conventionally used for fixing the cover:
(1) method of engaging a flange formed in the cover;
(2) method wherein the cover is slid into and interfitted with a groove; and
(3) method of ultrasonic welding.
In method (1), the cover 201 is fixed by coating a sealing material (not shown) on the side surface of the perimeter of a rectangular cover 201 wherein flanges 202 are formed at both end parts in the longitudinal direction, as shown in FIG. 23 a and FIG. 23b, and, by fitting the cover 201 into the opening 101a of the inner plate of the segment, as shown in FIG. 24, then elastically deforming each of the flanges 202 and engaging them to the respective engaging holes 204 formed in the side plates 203 of the segment facing both ends of the opening 101a. 
In method (2), the cover is fixed by forming a groove in both side edges along the longitudinal direction of the opening, forming protruding parts on both side edges along the longitudinal direction of the cover, coating a sealing material on the side surface of the perimeter of the cover, then inserting the protruding parts of the cover into the grooves of the opening, and sliding and engaging the cover to the back in the longitudinal direction.
In method (3), the cover is fixed by fitting the cover into the opening, and then ultrasonically welding the peripheral edge part of the cover to the peripheral edge part of the opening.
In the abovementioned fixing method (1), clearance is needed between each flange 202 and the engaging surface of a respective engaging hole 204, as shown by the enlargement of the engaging portion on the upper right side of FIG. 24, in order to elastically deform and engage the flanges 202 of the cover 201. If this clearance is absent, then the flanges 202 do not successfully engage with the engaging surfaces of the engaging holes 204, and they unfortunately disengage easily.
If, however, the abovementioned clearance is present, the pressure from the filler is applied downward to the cover 201 in FIG. 24 when the filler is filled in the gap between the outer periphery of the rehabilitating pipe and the inner wall surface of the existing pipe after assembly of the rehabilitating pipe. This causes the cover 201 to be displaced downward by just the portion of the abovementioned clearance. A gap is thus created between the side surface of the peripheral edge of the cover 201 and the inner surface of the peripheral edge of the opening, and the watertightness in the opening portion may no longer be able to be maintained.
In addition, in the fixing method (2), when interfitting the protruding parts of the cover to the grooves of the opening and sliding the cover all the way in the longitudinal direction, the sealing material coated on both side edges of the cover may unfortunately delaminate due to the sliding, and the sealing effect may unfortunately be markedly impaired. In addition, clearance is also needed for interfitting between the protruding parts and the grooves, and the maintenance of watertightness in the opening portion unfortunately degrades.
In addition, the fixing method (3), based on ultrasonic welding, is effective only if ring assembly is performed as shown in FIG. 20, and there is a problem in that it cannot be applied to segmental assembly as shown in FIG. 21 or FIG. 22.
The present invention solves the abovementioned problems, and has an object to provide a fixing structure that, in segments for the rehabilitating pipe assembly, fixes a cover to an opening for performing the work of mutually coupling segments in a direction corresponding to the circumferential direction of the rehabilitating pipe, and that can ensure sufficient watertightness in the portion of the opening plugged by the fixing of the cover, as well as that can be applied to both ring assembly and segmental assembly of the rehabilitating pipe.